Machinery condition monitoring is commonly performed in the machining industry as an effort to wholly utilize the useful life of machinery and the mechanical devices associated therewith. Failing rotating machinery in a complex machine such as a vehicle transmission can cause damage to other machine components, and sometimes necessitate replacement of the entire machine instead of the failed rotating machinery. Faulty rotating machinery should consequently be discovered and replaced before it fails. In some industries, gearboxes are routinely and periodically inspected, and gears or blades are often replaced at set periods of time even if a pending failure is not predicted. Inspections are costly, requiring many work hours as well as undesirable machine downtime and disassembly. Further, prematurely replacing gearboxes or individual gearbox components unnecessarily reduces their useful life.
In view of the needs for extending the useful life of rotating machinery and removing the risk of failure during use, technology has been developed for monitoring machinery while in use. For instance, there is currently a trend toward reusable launch vehicles that will require turbomachinery to operate for extended periods of time and on multiple missions.
Accelerometers are conventionally used to monitor rotating machinery and gears, and to determine operating performance and condition. Particular vibration signatures are related to specific types of component defects. For example, discrete gear tooth defects are often characterized in the frequency domain by the appearance of spectral components at higher order harmonics of the speed of the shaft upon which the faulty gear is located. The simplest fault detection techniques use a change in statistical properties of the vibration signal as a measure of engine health. However, the high operating speeds for engine turbopumps often render the data acquisition instrumentation incapable of measuring the vibration responses up to the gear mesh frequency.
Conventional methods for monitoring rotating machinery are also inadequate for continuously measuring fatigue level and gear chattering in real time. Further, such methods are inadequate for directly measuring gear tooth stress as it meshes with another gear. Accelerometers unfortunately respond to the combined resonances of all the components in the gearbox, including other gears, the housing, the gear shafts, bearings, and any other moving components. The inability of accelerometers to isolate the gear tooth resonances complicates fault detection.
Accordingly, it is desirable to provide a real time machinery health management system that directly monitors gear chattering and individual gear tooth deflection resonance amplitude, frequency, and duration. In addition, it is desirable to provide such a system that determines the fatigue level of each gear tooth and predicts the imminence of a failure in real time. It is also desirable for the system to be non-intrusive so the system remains intact when machinery parts are being replaced, lubricated, and cleaned, etc. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.